The fuel supply system for an internal combustion engine mounted on an automobile is provided with a pump and a pressure regulator. The pump feeds fuel to a fuel injection valve through a fuel pipe upon pumping the fuel from within a fuel tank. The pressure regulator prevents an excessive increase in fuel pressure within the fuel pipe that is regulated by operating the pump. One known example of this kind of pressure regulator is described in Patent Document 1.
The pressure regulator has a fuel channel for returning the fuel from within the fuel pipe back to the fuel tank. Also, the pressure regulator is provided with a moving part, which is displaced by force produced by the fuel pressure within the fuel pipe. The pressure regulator varies the flow rate of the fuel in accordance with the position of the moving part when the fuel is returned from the fuel pipe to the fuel tank through the fuel channel. Specifically, the amount of fuel that flows from the fuel pipe to the fuel tank through the fuel channel is increased by a displacement of the moving part caused by an increase in the fuel pressure within the fuel pipe.
In the event of an excessive increase in the fuel pressure within the fuel pipe that is regulated by operating the pump, provision of the aforementioned pressure regulator in the fuel supply system serves to increase the flow rate of the fuel that flows from the fuel pipe to the fuel tank through the fuel channel as a result of the displacement of the moving part caused by the increase in the fuel pressure, thereby, preventing excess increase in fuel pressure within the fuel pipe.